The present invention relates to a rail and guidance system for an elevator car, and more particularly to a concrete rail and a guidance system suitable therefor.
Elevator cars are typically guided between a pair of ferrous rails, such as steel, that are mounted vertically within a hoistway of a building. Rollers mounted to the car typically contact the rails and provide the car with a proper position within the hoistway. The rails are also used as fail-safe braking surfaces for emergency stops. In normal operation, the vertical motion of the elevator and all of the arresting of that motion is caused by the hoist ropes, which are moved upwardly and downwardly, and directed by means of a sheave. The ropes are also connected to a counterweight to provide mechanical advantage for moving and stopping the elevator car. The motion of the sheave is controlled by the elevator drive motor and the machine brake which are mechanically coupled to the sheave. Machine brakes typically are spring actuated into the braking position against a drum or a disk attached to the sheave, and use electromagnets to release the brakes from the braking position when the elevator is to move. This provides emergency braking insofar as electrical power or electronic signaling or an elevator safety circuit is concerned.
The steel rails of a typical elevator system are mounted to the hoistway by a series of horizontal supports. Many hoistways are typically comprised of concrete material and are either slip formed or poured in sections and assembled into a stack. The horizontal supports are subsequently attached to the hoistway by known methods and the rails are attached thereto using fasteners that allow the rails to be adjusted horizontally for malalignment. The rails must be manufactured and positioned within the hoistway to strict tolerances to maintain ride quality and uniform safety braking. It is especially difficult to maintain the necessary tolerances and placement of the rails as the building and hoistway tend to move and shift independent of the rails, such as during building compression, sway, thermal expansion or earthquakes. This movement makes it difficult to mount an elevator machine on the rails, which would allow a machine to be placed in an elevator hoistway. Another problem caused by rails being independent of the building is that divider beams must be added between elevators in a multiple hoistway or intervals that are typically 2.5 m which is less than the normal floor-to-floor distance in an office building. This is to provide support for the loads imposed by elevator safety devices.
Another problem with the use of steel rails is their impact on the environment during steel production and transportation and the difficulty in milling the rails to a standard shape within the prescribed tolerances. For each elevator, four (4) runs of steel rails must be provided to cover both sides of the car and counterweight. The weight of each rail ranges from 12 kg/m to 34 kg/m and rails are provided in 5 m sections. Another problem is worker safety because the rail sections must be hoisted, installed and aligned up all elevator hoistways.
The above mentioned rollers are a cause of unwanted noise in higher speed elevators as the rollers are constantly in contact with the rails and rotate at high speed and the friction from roller systems causes energy losses in the elevator system. A prior art elevator system avoids this noise by utilizing electromagnetic guides mounted to the elevator to position the car side to side and front to back within the hoistway. The electromagnetic guides provide a varying amount of electromagnetic force against the ferrous rails to position the car near the center of the hoistway while it is traveling either up or down. Electromagnetic guides require a significant amount of electrical power; in one example 1-2 kW is required to generate the forces necessary to maintain the car in the center of the hoistway.
One problem with prior art rails is that elevator safeties can damage the ferrous rails requiring expensive and time consuming repairs, which includes re-alignment of the rails and sometimes damage to the building after emergency stops and tests.
It is becoming typical in composite building construction to include a generally open rectangular concrete elevator core for buildings. This is due, in part, to the development of high compressive strength concrete. A common method of constructing these cores is generally that of xe2x80x9cslip-formxe2x80x9d construction where 3 to all 4 walls of a hoistway are poured in a progressive fashion top to bottom, either by pumping the concrete to the top of the building or by lifting hoppers to the top and dumping concrete in the form. The form may be jacked from a pocket in a cured section of the core below. In lower rise buildings pre-cast sections of concrete hoistways may be hoisted, aligned and staged in place.
In all of the prior art constructions the rails are metallic and therefore the elevator systems suffer from the drawbacks noted above. Alternatives to such rails therefore are desirable to the elevator art.
The present invention is a non ferrous guide rail and elevator guide system. In accordance with the present invention, guide rails are provided integrally with the structure of the hoistway and preferably comprise concrete material. The rails are formed as a part of the manufacture of the hoistway either during the slip form process or as part of the precast process. An embodiment of the elevator guide system of the present invention includes a plurality of air cushions positioned on the elevator car proximate the concrete rails. During vertical travel of the elevator car the air cushions are controlled to project a stream of air toward each surface of at least one and preferably all of the rails, and at least the car rails, and to produce a biasing force between each rail and the car. The air is provided by a fan or other source. The streams of air against the various surfaces position the car within the center of each shaft the hoistway providing a smooth and quiet ascent and descent. In one embodiment of the present invention each of the air cushions comprise a plurality of orifices having a seal positioned between the car and the rail to contain or restrict the flow of air therebetween. Another embodiment of the invention includes a control system which comprises a variable orifice controlled by a controller to vary the amount of air being emitted from each individual air cushion. In another embodiment, a controller controls the output of a fan or other air source to vary the amount of air emitted from each air cushion. In another embodiment a self-regulating valve assembly regulates the air flow to each air cushion to keep the car centered about the rail. The biasing force produced by each air cushion is proportional to the air pressure maintained within the air cushion. In another embodiment, conventional rollers or pneumatic tires are included to guide the car or counterweight in lieu of one of these air cushion systems, especially for the counterweight where xe2x80x9cride qualityxe2x80x9d is much less important.
In another embodiment of the invention, an inclined elevator or people mover is illuminated schematically. The system in the illustration is similar to a conventional inclined elevator in broad review but employs concrete guide rails that are integrally formed as in the prior discussed embodiments of the invention. The inclined elevator system of the invention employs air cushions for higher speed applications and rollers/tires for lower speed applications.